The Fiherenana River runs through the dry country around Toliara and helps explain why settlement and farming cluster where they do. In the dry season it can look more like a sandy corridor than a river, which is part of the southwest's stark charm.
It is not a standalone must-see, but it is a good landscape marker on local drives and excursions. Watch how quickly the city gives way to thorny scrub, riverbeds, and villages adapted to a much drier Madagascar.